Polymer compositions containing talc filler, polar organic compound and antioxidant

ABSTRACT

IN POLYPROPYLENE COMPOSITIONS CONTAINING SUBSTANTIAL AMOUNTS OF TALC AS FILLER, THE TALC SERIOUSLY DECREASES THE OXIDATION STABILITY OF COMPOSITIONS CONTAINING CONVENTIONAL ANTIOXIDANT SYSTEMS. IT HAS BEEN FOUND THAT THIS DEGRADING EFFECT IS DUE TO SELECTIVE SORPTION OF THE ANTIOXIDANTS ON THE TALC WHILE THE POLYMER COMPOSITION IS MELTED, AS IT NORMALLY IS DURING SOME STAGES OF PROCESSING. ACCORDING TO THIS INVENTION, THE STABILITY OF TALC-FILLED POLYPROPYLENE OR OTHER HYDROCARBON POLYMER COMPOSITIONS IS PRESERVED BY INCLUDING AS A &#34;TALC-DEACTIVATOR&#34; A POLAR ORGANIC COMPOUND WHICH IS SELECTIVELY SORBED ON THE TALC TO THE SUBSTANTIAL EXCLUSION OF THE ANTIOXIDANTS PRESENT IN THE COMPOSITON, WHILE NOT EXERTING A DEGRADING ACTION ON THE POLYMER COMPOSITION.

United States Patent 3,553,158 POLYMER COMPOSITIONS CONTAINING TALCFILLER, POLAR ORGANIC COMPOUND AND ANTIOXIDANT Evelyn G. Gilfillan,Audubon, N.J., assignor to Shell Oil Company, New York, N.Y., acorporation of Delaware No Drawing. Filed Aug. 30, 1968, Ser. No.756,425 Int. Cl. C08f 45/04, 45/58 US. Cl. 260-41 13 Claims ABSTRACT OFTHE DISCLOSURE In polypropylene compositions containing substantialamounts of talc as filler, the talc seriously decreases the oxidationstability of compositions containing conventional antioxidant systems.It has been found that this degrading effect is due to selectivesorption of the antioxidants ou the talc while the polymer compositionis melted, as it normally is during some stages of processing. Accordingto this invention, the stability of talc-filled polypropylene or otherhydrocarbon polymer compositions is preserved by including as atalc-deactivator a polar organic compound which is selectively sorbed onthe talc to the substantial exclusion of the antioxidants present in thecomposition, while not exerting a degrading action on the polymercomposition.

The inclusion of talc as a filler in polyolefin compositions isdesirable for various reasons. Certain talc-filled compositions, forexample, have been disclosed by Fischer in US. Pat. 3,157,614 to haveincreased dielectric strength due to the inclusion of a selected type oftalc.

Particularly useful are compositions in which the sole or predominantpolymeric component is polypropylene or a modified polypropylene. Suchcompositions exhibit greater stiffness and superior retention ofphysical properties at elevated temperatures, if properly stabilized,than polypropylene itself. Due to its relatively high heat distortiontemperature, polypropylene is useful in applications in which it may beexposed to the atmosphere at relatively high temperatures. It isdesirable that polymers intended for such uses have a high end usestability. It is also known that polypropylene itself is subject torapid degradation under the influence of oxygen at elevatedtemperatures. This degradation is largely prevented by inclusion ofantioxidant stabilizer compositions in the polymer. Stability againstdegradation due to the action of oxygen at elevated temperatures isgenerally designated thermal stability.

Many antioxidant stabilizers and stabilizer systems for polyolefins havebeen in patents and other literature, and a variety of such compoundsare in commercial use. The combinations which have found widestacceptance consist of a primary antioxidant, e.g., a hindered phenoliccompound, and a secondary or synergistic antioxidant, e.g., an alkylthiodipropionate. The primary antioxidant acts as a free radicalscavenger or chain terminating agent; the secondary antioxidant isgenerally believed to function through a mechanism of peroxidedecomposition. Different combinations of various primary and secondaryantioxidants are used to impart the various desired levels of oxidativestability to polymer compositions intended for different uses and hencerequiring'different degrees of stability against oxidative degradation.

3,553,158 Patented Jan. 5, 1971 The addition of talc in substantialamounts to polypropylene com-positions stabilized against thermaldegradation was found to drastically reduce the thermal stability of thefilled compositions, often to a level no higher than that of theunstabilized polymer. It is the primary object of the present inventionto provide a method for restoring the thermal stability of polyolefincompositions containing talc as an added component, and to providethermally stable talc-filled polyolefin compositions, particularly thosein which polypropylene or a modified polypropylene is the sole ordominant polymer component.

It was found in studies of the effect of talc as a filler inpolypropylene that the addition of 67 phr. (parts per hundred parts ofresin, by weight) of various types of talcs to a thermally stabilizedpolypropylene composition reduced the oxidation stability 1 of thecomposition by 70 to 98%, depending upon the type of talc used.

No explanation had heretofore been given for such a drastic degradingeffect due to talc, and several hypotheses were available as to possiblemechanisms. Depending on the mechanism involved, different measureswould be required to counteract the effect.

A prime candidate for the cause of the degrading ef fect of added talcwas the presence of metal compounds as impurities in the talc, whichmight function as prodegradants by promoting hydroperoxidedecompositions to free radical products. This effect should becompensable by the addition of metal-complexing agents. To test thishypothesis, a number of compounds which are known to act as metalcomplexing agents in polymers were added to talc-filled stabilizedpolypropylene compositions and their effectiveness in improving theoxidation stability of the mixtures tested. The observed differences ineffectiveness did not appear to be related to intrinsic complexingability. It was also found that there was no apparent correlationbetween stability and contaminant level. This suggested that thosecomplexing agents which proved effective did not owe their effectivenessto their metalcomplexing ability.

A second possible hypothesis to explain the degrading effect of talc wasto ascribe the effect to the changes in efficacy of the stabilizers dueto the high alkalinity of the talc. If this were the prevailingmechanism, it would be expected that addition of acidic compounds wouldbe most effective in counteracting the degrading effect. In testing ofnumerous compounds, no such correlation with acidity was observed.

A third possible hypothesis to explain the degrading effect of talc wasthat adsorption of oxygen on the talc particles resulted in a higherthan normal oxygen concentration in the polymer. This effect would beexpected to correlate directly with the talc particle size, but no suchcorrelation was observed in a study of six different talcs, havingaverage particle sizes from 0.5 to 7 microns.

Further studies suggested still another mechanism, which is believed tobe the predominant one in the degrading action of talc on oxidationstability of stabilized 1 Oxidation stability is reported, for purposesof the present disclosure and claims, as oven life at C. measured indays. The test is carried out by preparing plaques of specifiedthickness by compression molding and aging them to failure in acirculating air oven held at 150 C. The plaques are considered to failwhen surface powdering is observed. The test is run on at least threeplaques from each composition. The reported oxidation stability is themean oven life, in days, of all the tested plaques of a single thicknessprepared from a given formulation.

polyolefin compositions. It appears that conventional polyolefinstabilizers are sorbed on the surface of the added talc while thepolymer composition is in the melt state. Conversion to a melt andsubsequent solidification occur as process steps in the production ofstabilized, filled Melt flewgnig/io min. About4 polyolefin compositions,and generally also in the con- Den'sity at F 0 905 version thereof touseful articles as by injection molding, Tnsfle yi 4 extrusion, blowmolding, etc. Accordingly, the melted and a y 30 resolidified polymercompositions containing substantial X 1, amounts of talc are leftdefenseless against the attack 'Theiunstazblhzed'polymef f an Oven of yand of oxygen because most or all of the stabilizer is firmly y Whentestfid 10 II1 11 and 11011111 P q s held by the talc. p h y, at

It has now been found that a variety of organic polar COIIIPOSIUOI'IS ypy P p y X compounds can counteract this sorption mechanism by p w r p ypp n talc; and Specified WPQ and being themselves preferentially sorbedby the talc. For m un ofstabilzizers and talcdeactivatofs slgmoidpurposes of convenient reference, such effective comblade t ry yp mixer(Bfabendef Plasticqrder) under pounds are herein designated talcdeactivators. :ni rogep l gfl of e formulation It is thought that thesorption of both the antioxidant molded Into Plaques of 10 and 110compounds and the talc deactivators is due to bonds h fi i 1 1 h tcreated between their polar functional groups and oxide or e a emp oye me examp es c arac enze hydroxyl groups on the talc surface, but it hasnot been Q possible, to date, to predict strictly on the basis ofchemical structure which organic polar compounds will be effective x31}talc deactivators and which will not. However, once the Average Fe+AImechanism is known, it is easy to select a group of comi, name 252 t???pounds of which the predominant number will prove to 0 t j be effective.The selection can be made either by empirical Desertalc 5 g 6 1 57testing or by determining the relative sorbability on talc B Mistron p 1U of the candidate compound and the desired antioxidant composition in ahydrocarbon solution. EXAMPLEI In addition to preferential sorbability,the effective talc This b mustrates the effectiveness of a number d a is als hav to be sufiicientl non-volatil to 1 r m a i iii the p blyme i'during processiri g. This facto r 'is f Polar-Organic FP astalF'fieactivating agent? in automatically taken into account whenoxidation stability pp-lypropyleli-e. composltlons cfmtammgs Parts bytesting is carried out by determining oven life at 150 C., Polypropylene2 e Welght of talc f since excessively volatile compounds are quicklylost under f igzfigi Zg g ggigb g g i si these condmons' benzene,.about.0.5 phr. of dialkylthiodipropionates and Another necessary quallty ofefiectlve talc deactivators 0 1" of calcium stearate g I v is theirability to act Without adversely affecting optical 4O N compofindsvere'tested as talmdeacfivators and odor characteristics of the polymercomposltion' in the above compositions the tests being for oven life wasfound for example that some .compounds which atl50 C both in 10 mil and110 mil plaques The order might otherwise be effective causeddlscoloration of the of indicated by these two tests'is most compositionduring Processing aging S compounds cases very similar the minordifferences probably being P acceptable for I thls Y i compomidsaccounted for by differences.in volatility. The data are fins are Zmc eft recorded in Table 1, the tale deactivators being listed indlbutyldithiocarbamate, sallcyhdene hydrazine of salicylic decreasingorder Of effectiveness, based on the 100 mil acid. plaque data. 7

The following examples are presented to lllustrate pre- In e absence oftalc the polypropylene composition ferred modes of practicing theinvention and also to prohad a oven lif f 1 days, tested on 110 milplaques vide some of the data underlying the above discussion of d d edon 10 mi plaques. In the presence f the mechanism y which thestabilizers d alc d talc and without talc deactivaton 'these valuesdecreased activators act. to 14 days and 9 days, respectively.

TABLE 1 Unless otherwise stated, the polymer'employed in theseexamplesis polypropylene prepared by polymerization of propylene bycontact'with a TiCl -aluminum alkyl cata-' lyst, and characterizedby'thefollowing properties? Talc deactivating compound Oven life at 150 C.

Conccntra- 110 mil 10 mil Type Name Trade name tion, phr. specimenspecimen Highly effective:

Polyepoxide Condensation products of 2,2-bis(4- hydroxyphenyl) propane[bisphenol A] and epichlorohydrin. Product of Durrans, melting point7585 C"... Epon resin 1002 1. 0 105 67 Product of Durrans, melting point75 C. Epon resin 1001. 1. 0 98 66 Amide N,N-ethylene-bis-stearamideMicrotomic 280 wax 1. 0 87 50 Polyepoxide- Liquid product, predominantlydiglycidyl Epon resin 828 1. 0 76 61 ether of bisphenol-A. I AmideCondensation products of diethanolamine and Alromine R 100 1.0 55

carboxylic acids. Aliphatic polyol Mannitol 1. 0 66 52 Mixture of sodiumbenzoate and sodium Aerosol OT-B. 1. 0 0t 45 dioctYl suliosuccanate. 7

Moderately efiective: p

Aliphatic polyol Glycerine 1. 0 58 45 Aliphatic polyol. Polyethyleneglycol M Carbowax 6000. r 1.0 54 35 Aliphatic polyol. ca. 400 Carbowax400.- 1. 0 49v 40 Acrylate polymer Polymethyl methacrylate '1. 0 49 47Amide N,N-disalicylidene-1,2-propane diamide duPout metal deactiyator."1. 0 47 .43- Amino benzoic acid O-amino benzoic acid .f p 1.0 43 37 7Amino benzoic acid. p-Aminobenzoic acid 1.0 43' 3 SulfideBis(dimethylthio-carbamyl)disulfide. 1. 0 A3 1 35 Polyepoxide. Eponresin 812 1.0 43 27 Aliphatic polyepoxide polymer or the filtrate,demonstrating that they had been EXAMPLE 2 effectively removed from thecomposition by the talc.

A series of experiments on the polymer composition of Example 3, withouttalc deactivator, demonstrated that polymer stability decreasedessentially monotonically as the concentration of tale A in thecomposition increased from to about 40%. It was also found that a smallamount of talc, up to about 10% of the composition, did not removesufficient antioxidant to significantly decrease the stability of thecomposition. The limit below which no significant effect is observedwill be different In a different series of experiments, utilizing thesame polymer and as in Example 1 and testing only on 110 mil plaques,compositions were tested in which some contained 40% wt. of talc A andsome 40% of talc' B.

In those compositions in which effective talc deactivators were present,the oven life of the compositions containing talc B was typically about50% of that of compositions containing talc A. 10

In the absence of talc, the composition had an oven life of 100 daysTalc A Fi 9 days and l B for different antioxidant types andproportions. to 2 days. In compositions contarmng 1 phr. of variouseffective talc deactivators, the oven life of the composi- This mvennonof partlcillar.utlhty when thc Polymer tions containing talc A wasbetween 44 and 52 while that 15 component the composltlon polypropylen?because of compositions containing talc B and identical talc h polymeris often employed m the pfoduqtlon of ardeactivators was between 21 and35. tlclefs 0 2 used {it eleyated temperatuyes l q Compounds which wereeffective talc deactivators in stablhty 1S esp ecu} l l' The mventlon 1Si y these compositions included p-aminobenzoic acid and useful InComposltlons m Whlch polypropylene 1s modip fied by the addition ofanother polymer, e.g., an elas- (Mbeta hidmxyethynglycme' tomer, toimpart impact resistance at low temperature, EXAMPLE 3 or in which thestructure of polypropylene is modified by inclusion of a smallproportion of another monomer Another group of polar organic compoundswas tested during polymerization, to provide a random copolymer forelfectiveness as talc deactivating agents in a differently or a blockcopolymer structure. These polymers are typistabilized polypropylenecomposition, consisting of 3 parts cally prepared with Ziegler-Nattatype catalysts, such as by weight polypropylene, 2 parts by weight oftale A, combinations of titanium trichloride and aluminum alkyls. and acombination of 0.1 phr. of l,3,5-trimethyl-2,4,6- They typically containless than p.p.m., often only atri(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, 0.25 phr. few p.p.m.,expressed as metal, of catalysts residue. The ofdilaurylthiodipropionate and 0.1 phr. calcium stearate. 30 invention isalso of use in other polyolefins, particularly These tests were carriedout only on 10 mil plaques. those which have good temperatureresistance, such as The composition has an oven life of 40 days in theabsence poly-(4-methylpentene-l). The polyolefins are a well of talc and2 days in the presence of 40% of talc A but known group of polymersgenerally derived from olefins without added talc deactivator. of 2-8carbon atoms per molecule. The invention is also The results of thetests are set out in Tabl 2, useful in other thermoplastic hydrocarbonpolymers, e.g.,

TABLE 2 Oven life at 150 C. Talc deactivating compound Conccntra- 110mil 10 mil Type Name Trade name tion, phr. specimen specimen Epoxide 1Octyl epoxystearate DrapleX 3.2 1.0 48 Ester Sucrose benzoate 1. 0 38Aliphatic amine Stearylamine Kemamine P990. 1. 0 36 Polyepoxide Liquidcondensation product oibisphenol-A and Epon resin 828 1.0 33

epichlorohydrin. Ester Polyethylene glycol dibenzoate Benzoflex P-2001.0 32 Polyester Polyester of M.W. ca. 1000 Plastolein 9722 1.0 32Aliphatic amine N ,N,N,-tetrakis(2-hydroxypropyl) ethylenedi- Quadrol1.0 30 Amide 012 15 535 Slip-eze 1.0 21 Polyether Poly(oxypr0pyleneglycol ethylene oxide) Pluronic L-3l 1. 0 2O polyethylene, polystyreneand ABS (acrylonitrile-buta- EXAMPLE 4 50 diene-styrene copolymer).

Talcs suitable for use as fillers in polypropylene and The abovepostulated mechanism of efieehvehess of similar hydocarbon polymercompositions vary in particle talc deactivators was studied in a seriesof experiments Shape, particle Size, and contaminant content. The f r ofwhich some representative results are reported herein. particle typesare fibr or foli ted li i or i The amount of Various compounds Sorbed ytale A lar, platy or micaceous, and granular. They are described from 104 molar Solutions of the Compounds in hexane, o0 in greater detail inthe literature, including the aboveat C, Was deteYInihed- It was foundthat Conventional mentioned Fischer patent U.S. 3,157,614. Fischerstates pelyolefih antioxidants Whleh Were hindered Phenols were that aplaty talc imparts certain desirable dielectric propsofbed to a moderateextent, and micfomole erties to the composition. Compositions accordingto the P gram of tale and Others, Which Contained ester or $111- presentinvention may contain talcs having any of the four fide linkages, Weresorbed to a more Substantial extent, types of particles. For reasons notconcerned with stability, ranging from to miefomoles P gram of tale- Theacicular-platy talc is preferred in some polypropylene latter value wasobtained on dilaurylthiodipropionate. It compositions. The amount oftalc employed in the pol was also found that the extent of sorptionincreases with mgr-filled composition i i bl i h range f 1 increasingtemperature of the experiment, and is less, at a to 0.8 part by weightper part of polymer, which c given temperature, in a more viscousliquid. responds to about 9 to about 44% by weight of the total Thattalc removes antioxidant from a polymer compocomposition. sition wasconfirmed by preparing a composition of the In providing stabilizedtalc-filled polymer compositions kind described in Example 3, but freeof talc deactivator, according to this invention, a wide variety ofantioxidant dissolving the polymer in hot xylene, removing thecompositions is available for choice, including numerous talc byfiltration, precipitating the polymer with heptane, commercial primaryand secondary antioxidants. It is and testing the polymer and thefiltrate by infrared and preferred to employ, to the extent that it isfeasible, antiultraviolet spectrophotometry for the presence of theoxidant stabilizers which are poorly sorbable on talc. It antioxidantswhich had originally been added. No evidence has been found thatantioxidants in which the only nonof the antioxidant components wasfound either in the hydrocarbon groups are hindered phenolic groups aresorbed to a lesser extent, at given conditions, than antioxidants whichcontain ester groups, and are therefore generally preferred as primaryantioxidants in compositions of this invention. The following areillustrative.

Preferred primary stabilizers are hindered phenols in which a branchedalkyl group, ,such as a tertiary butyl group, is attached to each of thetwo positions adjacent the phenolic -OH. Preferred antioxidants of thistype, and their combination with preferred secondary antioxidants, aredescribed in US. Pat. 3,190,852 to Doyle. That patent refers for moredetails of preferred primary antioxidants to US. 3,053,803 to Jaffe et211., 3,026,264 to Rocklin et al., 3,062,895 to Martin et al., and3,047,503 to Jatfe et al. The disclosures of these patents areincorporated herein by reference.

Effective antioxidant stabilizing compositions typically increase theoven life of the polymer from a value of less than about days, tested on110 mil plaques at 150 C., to over 40 days.

A preferred member of the group is 1,3,5-trimethyl- 2,4,6-tri(3,5 ditert-butyl-4-hydroxybenzyl)benzene. A more volatile hindered phenol,which may be employed as such or in combination with another primaryantioxidant, such as one of the above hindered phenols, is2,6-di-tert-butyl-4-methylphenol.

Other hindered phenols are 1,l,3-tris(3-methyl 4 hydroxy 5tert-butylphenyl)butane and dioctadecyl paracresol.

A primary antioxidant which is relatively more strongly sorbed by talcis the ester type antioxidant tetra-[3-(3, 5-di-tert butyl 4hydroxyphenyl)propionate] of pentaerythritol. Another ester typeantioxidant is octadecyl-3 (3, 5-di-tert-butyl-4-hydroxyphenylpropionate.

The preferred group of secondary stabilizers aredialkylthiodipropionates in which the alkyl groups typically are thelauryl or stearyl group, although the C or higher alkyl groups are alsosuitable. These and other suitable secondary antioxidants are describedin greater detail in said Doyle patent and are known to persons skilledin this art.

The tale deactivating compounds of the present invention can be selectedfrom a wide variety of organic polar compounds. Among the most effectiveand preferred are epoxides, particularly polyepoxides; amides; acrylatepolymers; and aliphatic polyols. These types of compounds are well knownto organic chemists and nothing would be added to this disclosure byenumerating large numbers of them. Preferred compounds of these typesare illustrated in Tables 1 and 2. Not all compounds of these types areequally effective, as will be evident from the examples.

In general, suitable talc deactivating compounds will have a molecularweight greater than about 300; will contain one or more polar groupssuch as epoxide, aliphatic hydroxyl, ester, amide, ether or sulfide; andwill preferably contain a non-polar organic group which makes them atleast moderately compatible with the polymer, such as lauryl or stearyl.

I claim as my invention:

1. The method of stabilizing against oxidative degradation a compositioncomprising a thermoplastic hydrocarbon polymer, talc filler andantioxidant of which:

(a) the talc-free polymer composition, Containing from about 0.01 toabout 5 phr. of an incorporated antioxidant stabilization composition,has an oven life measured at 150 C. on 110 mil thick plaques greaterthan 40 days; and

(b) the talc-containing polymer composition containing only saidantioxidant stabilization composition has an oven life less than about50% of that of said talc-free polymer composition;

which comprises incorporating in the total composition, prior to amelting and solidification step, from 0.1 to 5 phr. of atalc-deactivating organic compound which is not itself suflicient tosubstantially improve the anti-oxidant stability of said stabilizedcomposition in the absence of said talc but is effective to improve theoven life of said composition to a value above about 40 days when thecomposition contains said talc, said organic compound being selectedfrom the group consisting of polar organic compounds which contain atleast one of the following polar groupsyepoxide, aliphatic hydroxyl,ester, amide, ether and sulfide, have a molecular weight in excess of300, are selectively sorbed by said tale in the presence of saidantioxidant stabilization composition while the polymer composition ismetled, and do not discolor said polymer during processing.

2. The method according to claim 1 in which said polymer ispolypropylene, said talc is an acicular-platy talc, present in an amountin excess of 10% by weight of the composition, said antioxidantcomposition comprises essentially a phenolic primary antioxidant and adialkylthiodipropionate, and said talc-deactivating compound is selectedfrom the group consisting of polyepoxides, amides, acrylate polymers andaliphatic polyols.

3. An oxidative-degradation stable composition comprising athermoplastic hydrocarbon polymer, from 0.1 to about 0.8 parts by weightof talc per part of polymer, and

(a) a combination of antioxidant stabilizers which, in

the absence of said talc, stabilize said composition against oxidationas indicated by an increase in its oven life to at least about 40 daysand in the presence of said talc increase the oven life of saidcomposition measured at 150 C. on 110 mil thick plaques to less than 50%of the oven life in the absence of said talc; and

(b) from 0.1 to 5 phr., suflicient, in combination with said combinationof antioxidant stabilizers, to increase the oven life of saidtalc-containing composition to at least about 40 days, of an organiccompound selected from the group consisting of polar organic compoundswhich contain at least one of the following polar groups: epoxide,aliphatic hydroxyl, ester, amide, ether and sulfide, have a molecularweight in excess of 300, are selectively sorbed by said tale in thepresence of said antioxidant stabilization composition while the polymercomposition is melted, and do not discolor said polymer duringprocessing. 4. A composition according to claim 3 in which said polymeris polypropylene, said talc is an acicular-platy talc, said combinationof antioxidant stabilizers comprises essentially a phenolic primaryantioxidant and a dialkylthiodipropionate, and said talc-deactivatingcompound is selected from the group consisting of polyepoxides, amides,acrylate polymers and aliphatic polyols.

5. An oxidative-degradation-stable polypropylene composition comprising,per 100 parts by weight of solid polypropylene: V

(a) from 10 to parts by weight of talc, (b) from about 0.01 to about 5phr. of an antioxidant stabilization composition comprising:

(i) at least one primary antioxidant selected from the group' consistingof 1,3,5-trirnethyl-2,4,6- tri(3,5-di-tert-butyl4 hydroxybenzyl)benzene; 2,6-di-tert-butyl-4-methylphenol; 1,1,3 tris(3- methyl 4hydroxy-S-tert-butylphenyl)butane; dioctadecyl paracresol; tetra [3 3,5-di-tert-butyl- 4-hydroxyphenyl) propionate] of pentaerythritol; andoctadecyl-3 (3,S-di-tert-butyl-4-hydroxyphenyl)propionate; and

(ii) at least one secondary antioxidant selected from thedialkylpropionates in which the alkyl groups contain from 12 to 18carbon atoms per p v molecule; and V (c) from 0.1"to 5 phr. of atalc-deactivating organic compound selected from the group consisting ofpolyepoxides, amides, acrylate polymers and aliphatic polyols which areselectively sorbed by said talc in the presence of said antioxidantstabilization composition while the polymer composition is melted andwhich do not discolor said polymer during processing.

6. A composition according to claim 5 in which said talc-deactivatingcompound is a polyepoxide condensation product of2,2-bis-(4-hydroxyphenyl) propane and epichlorohydrin, selected fromthose which are liquid at ambient temperature and those having a Durransmelting point not in excess of 85 C.

7. A composition according to claim 6 in which said primary antioxidantis 1,3,5 trimethyl-2,4,6-tri-(3,5-ditert-butyl-4-hydroxybenzyl) benzene.

8. A composition according to claim 6 in which said primary antioxidantis a mixture of 1,3,5-trimethyl-2,4,6-tri-(3,S-di-tert-butyl-4-hydroxybenzyl) benzene and 2,6-di-tert-butyl-4-methylphenol.

9. A composition according to claim 6 in which said primary antioxidantis tetra-[3(3,5 di-tert-butyl-4-hydroxyphenyl)propionate] ofpentaerythritol.

10. A composition according to claim 6 in which said primary antioxidantis a mixture of tetra-[3(3,5-di-tert- 10butyl-4-hydroxyphenyl)propionate] of pentaerythritol and2,6-di-tert-butyl-4-methylphenol.

11. A composition according to claim 6 in which said tale isacicular-platy talc.

12. A composition according to claim 8 in which said talc isacicular-platy talc.

13. A composition according to claim 10 in which said talc isacicular-platy talc. I

References Cited UNITED STATES PATENTS 3,157,614 11/1964 Fischer 260-4l3,425,980 2/1969 Baum 260-41 MORRIS LIEBMAN, Primary Examiner J. HDERRINGTON, Assistant Examiner US Cl. X.R.

